Fossil fuels, such as coal and gasoline, currently provide most of the energy needs of the world—including the United States. Moreover, the demand for fossil fuels has steadily increased over the years. At the time of the Oil Embargo of 1973, the U.S. net oil import rate was only one-third of total consumption, whereas today the U.S. net oil import rate approaches two-thirds of total consumption. With the U.S. oil consumption rate increasing by approximately 11 percent over the past ten years, and with crude oil spot prices have been recorded well over $140 per barrel, the U.S. economy is faced with a fuel bill approaching $700 billion over the next decade.
Because of the diminishing reserves and increasing costs of fossil fuels, as well as the damaging effects fossil fuels can have on the environment, alternative energy sources that are renewable and less damaging to the environment are currently being developed. Alternative energy sources generally include natural gas, wind energy, hydroelectric power, solar energy, hydrogen, nuclear energy and biofuels.
Although natural gas is a fossil fuel that burns cleaner than gasoline, it produces carbon dioxide—the primary greenhouse gas. Wind energy, one of the oldest and cleanest forms of energy, is unsightly and noisy. Hydroelectric power, an old and well-developed energy source, has a limited capacity for expansion. All energy (other than nuclear energy) is ultimately derived from solar energy, which can also be gathered directly using photoelectric cells. Hydrogen has proven to be a viable fuel source for vehicles, with the advent of fuel cells. However, use of hydrogen as an energy source poses problems with respect to its production, storage and distribution. Nuclear energy includes nuclear fission, which is very costly and generates toxic waste, and nuclear fusion, which is clean but has proven unworkable.
Biofuel is commonly defined as a solid, liquid or gas fuel derived from recently living organisms, including plants, animals and their byproducts. It is a renewable energy source based on the carbon cycle, unlike other natural resources such as petroleum, coal and nuclear fuels. Biofuels can be obtained from wood, single- and multi-cellular plant materials, animal excrement and bacteria. Ethanol is one type of biofuel that, combined with gasoline, is widely used in the transportation industry. Since biofuels can also be derived from plant oils, algae-derived biofuels have proven to be a promising alternative energy source. However, various obstacles have thwarted the large-scale manufacture and use of algal biofuels.
A primary obstacle inherent to conventional algal fuel production is the inability to produce and harvest algae in sufficient quantities to provide enough algal fuel to serve the energy needs of civilization. Utilizing existing methods, production of algal fuel in sufficient quantities would require growing algae in large production ponds or photo-bioreactors, each of which is limited by production and economic inefficiencies. It is estimated that approximately 200,000 hectares (approximately 450,000 acres or 780 square miles) of production pond surface area would be required to produce a quantity of algal biodiesel sufficient to replace the quantity of oil currently consumed each year in the United States.
Algae feedstock grown in open pond systems are subject to many systemic inefficiencies and challenges, some of which are also common to both open and closed system photobioreactor systems. Some of these challenges include the controllability of spectrum, intensity and duration of light cycles; temperature controls or seasonal temperature variations; contamination by hostile windborne particulate; and the cost of harvesting, transport, pre-treatment and storage, to name a few. These and other related challenges of conventional algae farming methods effectively limit the commercial viability of algal fuels.
Closed system photo-bioreactors, another conventional algal fuel production system, suffer from many of the same limitations, drawbacks and disadvantages, associated with open pond systems. For example, known closed photo-bioreactor systems preclude adequate control of light quantity, spectrum, duration and cycle. Additional issues include land area requirements, supporting and foundational structure requirements for large scale production applications, and harvesting inefficiencies. While closed system photo-bioreactors overcome, or substantially mitigate, many of the environmental and biological issues associated with open pond systems, they have not yet achieved an adequate level of efficiency required to produce algal biomass in quantities sufficient to reduce national dependence on foreign oil.
Accordingly, there is an unmet need for an algae bioproduct production and harvesting apparatus suitable for the mass production and harvesting of algae. What is needed is an apparatus that overcomes the aforementioned limitations, disadvantages and drawbacks, concomitant with open pond systems, closed-apparatus photo-bioreactors, and other known systems. It would be desirable to provide such an apparatus that enables greatly improved control over algae light exposure variables, including, for example, control over light cycle, light quantity, light spectrum and light duration. It would be further desirable to provide such an apparatus that also enables and facilitates precise monitoring and control of other variables that are known to affect algae growth rate, including, for example, algae temperature exposure, nutrient levels, and gas (e.g., O2 and CO2) levels. In order to address the aforementioned land requirement issues associated with existing open pond systems and closed system photo-bioreactors, it would be highly desirable to provide an apparatus having a structural configuration requiring a smaller footprint vis-à-vis existing systems. In short, it would be highly desirable to provide an apparatus that is low cost, easy to maintain, easy to reproduce, and that enables an operator to precisely control all aspects of the Calvin Cycle in order to maximize production and harvesting volume and efficiency, regardless of the desired strain of algae being grown.